Delay shot firing counters



Oct. 25, 1966 TsUGxo GoTo 3,281,626

DELAY SHOT FIRING COUNTERS Filed June 8, 1964 United States Patent O 3,281,626 DELAY SHOT FIRING COUNTERS Tsugio Goto, Nobeoka-shi, Japan, assignor to Asahi Kasei Kogyo Kabushiki Kaisha, Osaka, Japan, a corporation of Japan Filed June 8, 1964, Ser. No. 373,171 Claims priority, application Japan, July 12, 1963, 38/ 35,562 1 Claim. (Cl. 317-80) This invention relates to delay shot firing counters for counting bl-asting number of explosives.

The blasting number of single shots and del-ay shots of relatively long delay inte-rvals can be confirmed by counting the sounds of explosion with human ears, but in case of -milli-second delay shots, it is impossible rfor the ope-ra-tor to confirm the blasting number by listening to the sounds of explosion, and consequently, mis-tired shot can 7 not be detected, with the yfear of accidental explosion occurring later.

The present invention contemplates utilization of electri-c pulses that are generated at every blasting of explosives, for positively -counting or registering even shots of extremely short delay, such as milli-second delay shots.

When yan explosive is red, a plus or minus electric pulse is generated without exception. Such a pulse can be taken out from between the leg wire of electric detonator and the lground in case of electric shot firing. According to the present invention, the above-mentioned electric pulse is introduced into the counting circuit through the firing lead wire. However, the electric pulses generated by -ring of explosives are not even but different in individual explosions with respect to wave forms and durations, and their count cannot be taken as they stand, but each pulse should be converted to that of square waveform of a definite duration suitable for counting. Thus, according to the present invention, the delay shot -ring counter essentially comprises a blasting machine, a primary and a secondary square wave generators, and a counter, all combined into a unity organization.

An object of the p-resent invention is to provide a delay shot ring counter of such a small size and light weight that it may conveniently be portable, by utilization of transistor-type D.C.D.C. converter giving constant output with low voltage dry cell battery as the power source for blasting machine.

Another object of the present invention is to provide a delay shot iiring counter which always produces a constant output for blasting by employing in the blasting machine a constant voltage circuit comprising a transistor, -a .silicon diode, and a neon glow lamp.

Another object of the present invention is to provide a delay shot -ring counter employing in the blasting machine an arc discharge tube having a cold cathode as the blasting switch, Iand a discharge resistance of a low resistanoe value as small as one tenth to one thirtieth of that in a conventional condenser type electric blasting machine, say 1509, and having an electric neutral point, whereby the current having been supplied for blasting is completely eliminated trom all -the circuit connected to the tiring lead wire, before explosion of the rst stage electric detonator.

A 'further object of the present invention is to provide -a delay shot firing coun-"ter in which a primary square-wave voltage generating circuit is used for drawing out the electr-ic pulse produced by the blasting of explosive from the neutral point of fthe afore-mentioned discharge resistance independently of lthe blasting voltage, and yet, independently of its Ipola-rity, Ithe electric pulse produced by one explosion is converted without fail to a square-wave pulse of duration longer than the aboveJident-ied electric pulse.

Patented Oct. 25, 1966 A further object of lthe present invention is to provide a delay shot -ring counter in which a secondary squarewave voltage generating circuit is used for converting the blasting volt-age to a square-wave voltage of a duration longer Ithan that of the blasting voltage, the above-mentioned square-wave voltage being used -for clamping the aforementioned primary square-wave voltage generating cir-cuit.

A still further object of the present invention is to provide a delay shot ring counter for counting blasting number of explosives by an electric counter operated by the square-waive output pulses of the aforementioned primary square-wave voltage generating circuit.

Partioularities land details of the present invention Will be made obvious from the following descrip-tion of the invention, with reference to the accompanying drawing, in which the single `figure is a circuit diagram showing one embodiment of the present invention.

Referring to the drawing, the delay shot firing counter embodying the invention as a whole is accommodated in a casing 1 provided with blasting output terminals 2 and 3, and an earth terminal 4. 5 shown by dotted lines, is a switch and interconnects a power switch 6 for the counter and a blasting switch 56 mechanically. Thus, when the switch 5 is operated to the ON position of the counter power source, the counter switch 6 is closed, and the power sour-ce 7 consisting of three dry cells in series operates a transistor-type constant-output D.C.D.C. converter 8 for applying an anode Voltage of D.C. 350 v. to the dekatron of a counter 9, to place the counter 9 in operating state. In addition, the power source 7 acts to place a transistor-type square-wave arnplier 10 and a transistortype electric pulse amplifier 11 in operating conditions, and at the same time, places in standby states a primary square-wave voltage generating circuit formed by one shot multivibrator of 2.6 msec. interval of output square-wave, and consisting of transistors 12 and 13, resistances 14, 1S, 17, 18, 19, 20 and 21, a mp. condenser 15, and an electrolytic condenser 22; and a secondary square-wave voltage generating circuit formed by one short multivibrator of 8 msec. interval of output square-wave, and consisting of transistors 31 and 32, resistances 33, 34, 35, 37, 38, 39 and 40, a mp. condenser 36, and an electrolytic condenser 41.

When the switch 5 is actuated to the position of blasting charge, the power switch 6 for counting system is held at the ON position, while the blasting switch 56 is operated to open its contacts 57-58 and to close its contacts 57-59, whereupon a switching transistor circuit commences to operate for converting the low voltage dire-ct current of dry cells 62 to 'square-wave alternating current, the switching transistor circuit being consisting of switching transistors 60 and 61, the prima-ry winding 64 of a convertor and boosting transformer 63, the cont-acts 57-59 of 'blasting switch `56, the dry cells 62, three in series, a transistor 66 Iforming the base circuit of switching transistors 60 .and `61, resistances 67 and 68, a condenser 69, and a feedback winding 70 of trans-former 63. The -square-wave alternating current voltage thus produced is stepped up by the combined convertor and boosting transformer 63, and -the output of its secondary high tension winding 65 is -rectied to high tension direct current voltage by the voltage double rectification of a voltage doubler circuit consisting of silicon rectiiiers 71 and 71', and mp. conde-nse-rs 73 and 72, whereby a blasting condense-r 74 is charged up promptly.

When the terminal voltage of blasting condenser 74 thus charged has reached at 248 v. which is the control voltage of a constant-voltage silicon diode 75, that is 80% of the normal charging voltage, a controlled current of the contant voltage diode 75 flows through a resistance 76. A minute interval of time thereafter, or after about 1.5 to 3 seconds have elapsed from beginning of the charging, the terminal voltage of blasting condenser 74 reaches Iat substantially the normal voltage. At the same time, the terminal voltage of the resistance 76 .also reaches at the firing potential Iof a neon lamp 77 (NE 68), whereupon the Ilam-p 77 starts to discharge, and the disch-arge current of the same flows to the resistance 68 through a yresistance 78. The resistance 68 is connected between the |base and emitter of the current controlling transistor 66. The transistor 66 being connected in the base circuit of switching transistors 60 and 61, when the discharge current -flows through the resistance 68, the electric potential of the base with respect t-o the emitter of the transistor 66 drops abruptly by about 0.15 to 0.20 v. Thereupon, the emitter-collector current of control transistor y66, or the base current of switch-ing transistors 60 and 61 decreases, causing decrease in its collector current. Consequently, the electric energy of D.C. high voltage sent out to the D C. 'high tension circuit is also made small instantaneously, resulting practically in termination of charging of the blasting condenser 74.

On the other hand, when the electric energy having been supplied becomes equal to the electric energy consumed in the D.C. high tension circuit, the a'fore-mentioned current increase -in neon -lamp 77, the lowering of base potential of the transistor 66, and the decrease in collector currents of the switching transistors 60 and 61, are terminated automatically, and the terminal voltage of blasting condenser 74 is kept to a substantially constant D.C. voltage, independently of regulation of voltage of the power source 62.

Next, if the switch 5 is Ireturned t-o the blasting position, the bla-sting switch contacts -57-59 -a-re opened and the lbl-asting switch contacts 57-58 are closed, with the source switch 6 left at the ON position. Thereupon, the switching operation of transistors 60 and 61 stops, and the charge voltage of blasting condenser 74 is applied to the resistances 79 and 80. At this time, the potential difference between .grid 83 and cathode 84 of a cold cathode arc discharge tube 81 (SP `902) being about 1.5 times its ring potential, main arc dis-charge takes place between its anode and cathode, thus supplying the energy charged in the blasting condenser 74 to the electric detonator connected between blasting output terminals 2 and 3, through the cold cathode arc discharge t-ube 81. Between the blasting output terminals 2 and 3, a provision i-s made for drawing out electric pulses produced by explosions of the explosives independently of the blasting voltage, and a discharging resistance 85 is connected, which is of a small resistance va'lue as low as one tenth to one thirtieth of that for a conventional condense-r-type blasting machine, say 1509 or lower. This is for the purpose of completely eliminating the firing voltage Ifrom the 'blasting lead wires, electric detonator, and between the blasting output terminals 2 and 3, before explosion of the prima-ry explosive.

The electric .pulse -generated by explosion of the explosive is applied through the blasting lead wires across the blasting -output terminals 2, 3 and the earth terminal 4, and introduced into the electric pulse amplifier 11, through a combined amplitude limiter and band pass iilter 51 and a transformer 50 having the prima-ry and secondary windings insulated from each other. The electric -pulse having been amplified in t-he amplifier 11 is applied to the resistances 29 and 30 connected across the secondary winding of transformer 49, as substantially the same potential pulses of opposite polarities with respect to the earth 87. The one shot multivibrator (th-e primary square-wave voltage generating circuit) of 2.6 msec. interval of output square wave, consisting of transistors 12 and 13, starts to operate at the time when the voltage applied to the resistance 29 or 30 is of positive polarity with respect to the earth 87, and its crest value is more than 200 mv. (corresponding to 150 mv. between ter-v minals 2, 3, and 4), .and generates a single square wave pulse of 2.6 msec. duration for each input of the abovementioned polarity and va-lue. Thus, when the volta-ge applied to the resistance 29 is more than +200 mv. with respect to the earth 87, the pulse current owing through condenser 27, semicond-uctor diode 23, condenser 16, and resistance 15 renders the transistor 12 OFF and the transistor 13 ON, and this condition is sustained for 2.6 msec. Upon elapse of 2.6 msec., the transistor 12 returns to ON, and the transistor 13 to OFF, and the one shot multivibrator assumes the standby state automatically. When the input electric pulse is of the opposite polarity, that is, when the voltage applied to the resistance 30 is more than +200 mv., the pulse current flowing through condenser 28, germanium diode 2'4, condenser 16, and resistance 15 operates th-e one shot multivibrator in the same manner as mentioned above. The resistances 25 and 26, and germanium diodes 23 and 24 are provided for the purpose that the electric pulse applied to the resistance 29 or 30 is supplied to the one shot multivibrator, only when the pulse is of positive polarity with respect to the earth 87, `and the transistor 413 is OFF, in order to prevent erroneous counting caused by any Wrong operation of the one shot multivibrator.

When the one shot multivibrator is operated as abovementioned by the in-put electric pulse, there is a square wave output of .about k-4 v. in the resistance 14 connected to the collector of transistor 12. This square wave voltage is ampliiied by the transistor amplifier 10, and boosted by the transformer 48, to operate the counter `9 which count-s the number of incoming pulses, that is, the number of explosions of explosives.

Further, when firing voltage is applied between blasting output terminals 2 and 3, it is also applied to the resistances 53, 54 and 55, and the insulating transformer 52, and a pulse voltage of about +1 v. momentary peak voltage with respect to the earth 87 appears on the secondary side 88 of insulating transformer 52 at the instant of application of blasting voltage. This pulse voltage acts through condenser 44 and germanium diode 42 to operate the one shot multivibrator of the secondary square-wave voltage generating circuit having transistors 31 and 32 as the active elements. The interval of output square wave of the above multivibrator is 8 msec. This 8 msec. squarewave pulse output of the secondary square-wave voltage generating circuit changes the -0.1 v. potential at the joint point of resistances 45 and 47 connected to the collector of transistor 31` to -1 v. abruptly, which acts through germanium diode 46 for rendering'the transistor 13 of primary square-wave voltage generating circuit ON, thus clamping the primary square-wave voltage generating circuit in operating state during the operating period of the secondary square-Wave voltage generating circuit, that is for 8 msec. from application of the blasting voltage.` Consequently, during the above-mentioned period of time, the primary square-wave'voltage generating circuit operates only one time, `even if any other electric' pulses would come thereinto. As a result, the counters also do operate only one time during the same period, and this is to prevent erroneous counting caused by blasting voltage. Accordingly, the true number of firing of explosives is the count number of counter minus one in the delay' shot ring counter of the present invention.

Further, according to the presentinvention, the delay shot firing counter comprises transformers 50 and 52 for insulating the blasting machine from the earth 87, which is connected to the earth terminal 4 through a high resist` ance 86 and a condenser 56. When it is not necessary to insulate the blasting machine from the earth 87,' the terminals of high resistance 86 may be' short circuited.

Test I.-In 1.0-1.5 cm. deep of red earth, g, am-y monium gelatine dynamites wereloaded 4one or two per hole, and all were connected in series with conventional milli-second delay electric detonators. A 159 parallel resistance was externally connected with each detonator as input circuit for explosion pulse, and ground connections were made at two-metre distances from respective holes loaded with the dynamites.

Two rounds of tests were executed, with MS2-6 period 2.6 msec. duration which is longer than those of the input pulses. Consequently, even when the wave form of an electric pulse produced by explosion would be so complex that there may effectively be produced two or more electric pulses, the counter does never misoperate, but posidetonators in the irst test, and MS2-l0 period detonators 5 tively count one for one explosion. in the second. The explosions were elected and their In addition, according to the present invention, the number counted by a delay shot firing counter of the preslimit of voltage for electric-pulse counting is established ent invention. The results are shown in the table below. at 150 inv. between the blasting output terminals (2, 3)

Test No. Detonators used Number of Counted Number of Non-exploded blastings number explosions period 1 MS2-6 period 5 5 5 0 2 MS2-i0 period.--.- 9 s s 3rd In the second test, for 9 detonators, 8 explosions were and the earth terminal (4). This voltage value is detercounted, showing one non-explosion. mined with a sufficient allowance with regard to experi- Test II.-A hole of m. length were perforated into 20 mental data, taking into consideration the fact that eleca layer of coal of 2.4-3.2 in. and 180 g. ammonium nitrate tric pulses produced by explosion of explosives are of explosives of low density were loaded therein. Double varying voltage values to a large extent, so that misbridge type delay electric detonators of 30MS2-5 periods counting of number of explosions is fully prevented. were employed. Ground connections were set to iron It is also to be noted that, according to the present inpillars in the gallery by magnets. Double bridge type elecvention, the secondary square-wave voltage generating tric detonator makes it unnecessary to provide external circuit icomprising transistors 31 and 32 as the active eleconnection of parallel resistance as input circuit for exments is provided for converting blasting voltages into a plosion pulse. Distances between respective loaded posisquare-wave pulse of 8 msec. duration which is longer tions and the ground connections were 1.3 to 2.8 m. The than those of the blasting voltages, and primary squareresults are shown in the table below. wave voltage generating circuit is clamped with the output square-wave voltage of said secondary square-wave Test Number Counted Number Non. voltage generating circuit. As a result, the primary N0- Detonator used Maggi Humber fseX-n @Xrlggd square-wave voltage generating circuit can operate once g p o p only during the 8 msec. duration from the application of MS2 5 Steps 4 4 4 0 35 blasting voltage, thus preventing the counter from misd0 4 4 4 0 operation by virtue of electric noises.

g What I claim is: j: 4 3 3 4th A delay shot tiring Icounter comprising a blasting -----d0 g machine formed by an electric supply source consisting do 4 4 4 o 40 of transistor-type D.C.-D.C. convertor of a constant outdo g put voltage, a circuit of a transistor, a silicon diode and a neon lamp to obtain a constant voltage output for blasting, a blasting switch consisting of a cold cathode arc- Thus the delay shot rmg counter of the pl'eent lnvll' discharge tube, and a discharge resistance lower than 1509 non can count the true number. only of exploslves. which provided at the output thereof, a circuit so arranged that have actllally exploded any mlsred exploslve bemg de' electric pulses produced by explosion of explosives are tected Wltllut fall taken out from the electric neutral point of said discharge In addltloll the. delay Shot rmg Counter embodymg resistance, a primary square-wave voltage generating cirthe Present lnyentlon .hast as the. Power Source. for the cuit for converting each of said electric pulses into a blllstmg .machme a clrcult conslstmg of translstor 66 50 single square wave pulse of duration longer than said slllcon dlode 75 neon lamp 77 etc." so that a low Roten' rst mentioned electric pulses, a secondary square-wave tlal battery may be utlhzed electwely but there 18.110 Voltage generating circuit for converting a blasting voltage fear of mlsrmg due to Shorlag of Output for blastlng' into a square-wave voltage of duration longer than that Furlher the delay Sho? flung munter. of the present of said blasting voltage, for clamping said primary lsquareinvention can promptly eliminate the blasting voltage from Wave voltaoe e r t. ir it nd l t r ted the blasting circuit because of using the blasting switch b h b g ne a mg C Cll a f a. colin er ope a having a cold-cathode arc discharge tube and a discharge y t e Square'wave Olltputlu 56S o Sald pllmary Square' resistance 85 of lower than 15052 between blasting output Wave 'Oltage genera/ung clrcult for counfmg mlmber of terminals 2 and 3' Thus, the delay Shot firing counter of explosions of theexplosives at the same times with blastthe present invention ldoes never make miscount .by virtue mg of Sad eXPlOSlVeS- of blasting voltage or electric noise, if there were any shortcircuiting or grounding of blasting lead wires. References Cited by the Examiner izmhermdlg t tile-lrseIthci UNITED STATES PATENTS pu ses pro uce y exp osi n electric neutral point of the discharge resistance, and con- 2814991 12/1957 Canoe 1oz-22 sequently, the electric pulse detecting circuit is never 219 561226 10/1960 Vogt et al' 5524""73 affected bythe blasting Voltagg 2,961,583 11/ 1960 Sorensen 317-80 According to the present invention, it is also to be noted 31133231 5/1964 Fall et al 317-80 that the primary square-wave voltage generating circuit comprising transistors 12 and 13 as the active elements 70 RICHARD M WOOD P r mary Examiner converts input electric pulses to square-wave voltages of V. Y. MAYEWSKY, Assistant Examiner. 

